Stimulation of the right heart cavities is typically achieved by implanting endocardial probes by the right peripheral venous network. However, in order to stimulate the left heart cavities, one typically introduces the endocardial probe into the coronary network. For example, for an electrode laid out vis-à-vis the left ventricle, the access to the entry of the coronary sinus is done via the right atrium.
The installation of such a probe is a particularly delicate intervention, because the position of the points of stimulation is very important. Thus, in the case of a pacemaker of the “multisite” type, the left ventricle and the right ventricle points of stimulation must be as distant from one another as possible to optimize the resynchronization of the whole of the cardiac cavities. In the same way, the stimulation of the left atrium imposes a very precise positioning of the probe in the network of the coronary veins. Of course, when the selected site is reached, the maintenance of the probe in the selected position must be ensured for the long and short term, regardless of the size of the vein.
The published EP-A-0 993 840 and its counterpart U.S. Pat. No. 6,385,492 B1 (commonly assigned herewith to ELA Médical) describe a coronary probe that is equipped with various elastic structures likely to provide a retention function, for example, by means of a ball at the distal end, eventually inflatable, of a chain of spheres of increasing diameters, of an elastic skirt, etc. These various retention structures, although effective to ensure the desired retention in place, nevertheless have a relatively complex structure that makes their construction and implementation difficult. Furthermore, those retention structures are rather adapted to sectoral electrode probes, being conceived to ensure an elastic pressure between the probe and the internal wall of the vein on the side opposed to that of the sectoral electrode, so as to accentuate the pressure of the sectoral electrode against the wall of the vein. Moreover, these retention structures can make the probe difficult to extract or to reposition, except when also envisaging a relatively complex structure able to ensure the reversibility of the implantation, for example, by implementing deflatable balls or turned up barbs.
Indeed, once the probe is installed, it is desirable to be able to extract it or to reposition it without damaging the veins of the coronary network. This imposes a need for a retention system that is not very traumatic in its configuration. In the same way, at the time of the implantation, more specifically at the time of the progression of the probe, the surgeon must be able to cross, without too many difficulties, the obstacles such as valvules or junctions of the coronary network. The retention structure therefore, must not interfere significantly, if at all, with these operations.
Lastly, it is recognized that the retention structure be conceived to allow the introduction of a probe into the internal lumen of reduced diameter of a guiding-catheter as well as the use of an axial stylet along which one can slide the probe (the latter being a probe installation technique known as “wire-guided”).